Anyone use duct fans to pass heat?

Hi Everyone,

I have a 6" hole in my ceiling. No that's not a bad thing. It's directly above the stove, that passes into a room upstairs. Fortunately, it was left there by a previous owner... presumably to pass heat from a stove!

Yesterday, I went to HD and bought a "duct fan" to stick in the hole in an attempt to move heat from the stove area to the rooms upstairs. The fan claims 250 CFM. Unfortunately, after one day's worth of being on, there's very little difference in the real-feel temps upstairs. In fact, there seems to be just a little more air flow through the hole than there was with the natural heat rising prior to installing the fan. I do feel a breeze, but that's about it. I was hoping for the feeling of nice heat being blown through the hole, similar to a forced-air vent system.

Anyone else using duct fans for this purpose?

Any ideas as to how to make this hole more effective? Different kind of fan?

Thanks for any help you can give!

Thanks for the insight regarding code. Who would have thunk that one eensy hole would be such a big violation? Well, regardless of code abiders, I'll not likely be getting the plaster out any time soon to fill it. Plus, if it's already there, I might as well try to take advantage of it and get some heat traveling through it - for better or worse. Maybe there's a way to respect the code intent AND get a fan in there???? Any thoughts?

I'm rather surprised that I've had the building inspector over there, the installer, and several workers over there for stove estimates, and NONE of them mentioned a code violation. Plus, the fellow who installed it RECOMMENDED that I put the fan in there!

Yes, I do believe that some of the heat is radiating up there through the floors, but my thought was that it might be more than we feel. Fortunately, the upstairs does retain some of the heat, and the whole floor doesn't get much below 60 degrees up there, but for the sake of our young daughter, we were hoping for a few degrees warmer.

I'm wondering if anyone has used more powerful fans, and if that might make a difference? I really only feel a slight breeze coming up out of the hole, whereas, I was hoping for a good blast of air.

After reading another reply... I wonder if it might make sense to reverse the flow of my fan, and have the air from the upstairs room pulled down through the hole, toward the stove, leaving the room pressure in the upstairs room such that it would need to suck air out of the hallway, which leads to the stairs, where the most heat is coming up.

Russ in Chicagoland said:

There is one on ebay called Aero Flo.

The one you have going between floors doesn't feel like much when you hold your hand to it, but put a thermometer next to the opening in the bottom room and it's hard to argue against sucking 80 degree air and sending it into a 60 degree room. .

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Thanks for your thoughts...

What specifically makes you think that the Areo Flo would be much better than the one I got at HD?

You'd think if the one I got is supposed to move 250 CFM, that you'd feel a much bigger difference than I do. That's a lot of air moving around!

Yes, CO and smoke detectors are a must in any house. There's actually a C0 detector in the upstairs room, so if there's any problems, we should know quickly.


Thanks again, I may just order the fan you suggested, and do an A/B to see which one blows the most!

Hey Russ,

Thanks for more info, and the link. I actually thought about this fan before I stumbled across the one at Home Depot. I may try both out, as you did, then decide.

By the way, what is a "BX whip"? To connect mine, I simply connected the three leads off the fan to a 3 wire zip cable and plugged 'er in. Somehow, I suspect I'll get yelled at by people on here for doing that, and if someone puts up a good case, I may reconsider that, too! Any thoughts?

dispatcher101 said:

In terms of moving air faster, just realize that the faster the air travels the more heat it will lose.

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Hmmm... interesting point. Thanks for the thought.

Typically, heat moves to cold, right? I don't think heat can just go "poof" and it's gone... it has to end up somewhere. And if I get the theory correctly, even if the heat is moving faster, the heat should still dissipate in the room and change the energy level of the cold, thus making it feel overall warmer, albeit perhaps a little more subtly. I suspect, that when the air is moving slower, one could get the feeling of direct heat coming up through the hole by means of a direct path of warm air molecules, whereas when it's moving faster, the heat more quickly dissipates into the surrounding air, making the stream of air feel less "warm". Does that make any sense? I wonder. I'm just arm-chair philosophizing!

BeGreen said:

A bit of code guidance here:

R602.8 Fireblocking required. Fireblocking shall be provided
to cut off all concealed draft openings (both vertical and horizontal)
and to form an effective fire barrier between stories, and
between a top story and the roof space.

4. At openings around vents, pipes, ducts, cables and wires
at ceiling and floor level, with an approved material to
resist the free passage of flame and products of combustion.
5. For the fireblocking of chimneys and fireplaces, see Section
R1003.19.


2.3. Return-air inlets shall not be located
within 10 feet (3048 mm) of any appliance
firebox or draft hood in the same
room or space.
3. Rooms or spaces containing solid-fuel burning
appliances, provided that return-air inlets are
located not less than 10 feet (3048 mm) from
the firebox of such appliances.

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I wonder how we're interpreting this code. If you look at the first paragraph, it indicates the code is in reference to concealed spaces AND for providing a fireblock between stories. This could imply that the code references BOTH scenarios. This is also supported by #4, which says that openings around ducts, which may also include the hole created for the duct itself, whether filled or unfilled. This would likely preclude my "hole" from being legal.

If this isn't convincing, the points 2.3 and 3 also seem to make my little hole rather dubious. If, after all, the intent of this code is to prevent fire and gasses from spreading, my hole certainly doesn't help.